Yahoo CEO Marissa Mayer in recent weeks has repeated several points about the company’s turnaround strategy: Web search, porting Yahoo’s services to mobile devices, and investing in overseas markets must play a key role in its future growth.

At the Goldman Sachs Technology and Internet Conference in San Francisco, Mayer’s third public appearance in the past three weeks, the former Google executive reiterated her view on the opportunities and challenges facing the Internet pioneer, which has experienced flat or declining revenue for years.

Many of Yahoo’s key services, such as Yahoo Mail and Yahoo Search, have been losing share to rivals while even strong properties such as Yahoo Sports now face more competition than ever from the likes of ESPN and other sites.

Mayer said she was confident Yahoo could grow usage by succeeding through apps on mobile devices, even though the company doesn’t control a mobile operating system like Apple and Google’s Android software that it could use to steer people to its services.

First, Mayer said, Yahoo would reduce the number of mobile apps in its portfolio from more than 60 to about a dozen. Yahoo also will help its large PC-based sites such as Yahoo Groups and Yahoo Mail to be stronger on mobile devices, she said. Creating a robust video offering also will be important, she said.

“Yahoo has the content that people want on their phones,” she said, citing email, weather information, news, stock quotes and other “daily habits” for which Yahoo already has an app.

Mayer also touched upon Yahoo’s alliance with Microsoft, whose Bing search engine powers the Web searches and search-ads on Yahoo sites. While there have been “nice gains” in the revenue generated for every search done on Yahoo sites, the alliance hasn’t eaten into Google’s market share; rather, Bing.com has taken share away from Yahoo Search.

“We collectively need to grow share (at Google’s expense) rather than trade share between us,” Mayer said. The key to doing that was “innovation” in “user experience,” or how the search results appear, she said.

Mayer, who took over Yahoo last summer, also addressed another challenge for Yahoo—that it’s primarily domestic. She cited the U.K. and Germany as markets where “we do need to get stronger.” Yahoo also owns part of Yahoo Japan, which is an Internet powerhouse in that country, and has considered selling its stake in recent years. Mayer implied that a sale wasn’t in the cards, saying that Japan is “just such a rich market in terms of advertising…that it’s important that we play there.”

Also on Tuesday Yahoo announced its fourth acquisition of a small start-up since Mayer joined, this time of an iPhone and iPad app called “Alike” that helps people discover restaurants and other local businesses they might like. Alike has five employees. Yahoo didn’t reveal terms of the deal.